Malaria remains one of the most common diseases in the world, with about 300 to 500 million cases of malaria infection estimated to occur annually. Approximately 1.5 to 2.7 million patients die annually from malaria, among them one million children are less than 5 year old. This disease, the incidence of which has been increasing for last 5 years, is today a major impediment to social and economical development in many countries. In France, 3400 cases of malaria are detected yearly, with 80% of them due to Plasmodium falciparum. 
The pathogen agent of malaria is a protozoic parasite (Plasmodium) transmitted by the anopheles female to man, who is the intermediary host of the parasite. There are four types of plasmodium specific pathogen for human; Plasmodium falciparum, most frequently encountered in Africa, is occasionally fatal; Plasmodium vivax, Plasmodium malariae and Plasmodium ovale are not fatal, but may result in relapses.
The laboratory diagnosis of malaria is usually established by standard procedures that include thin and thick film examinations, based on the observation of intraerythrocytic parasites in the blood smear, and possible investigation for soluble specific antigens. However, these investigations are only undertaken if there is a clinical suspicion that a patient may actually have malaria. Although a high level of suspicion may exist in endemic areas for malaria, this is not always the case in nonendemic regions, particularly if there is a failure to take an adequate patient history. Even when there is a clinical suspicion, it is not uncommon for laboratories in nonendemic areas to have relatively poor expertise for detecting and identifying malaria. It has been reported that although a blood count is almost always requested as part of the routine investigation of febrile patients, changes in leukocyte and platelet parameters are rarely sufficiently distinctive to suggest directly a diagnosis of malaria (Kueh et al, 1982, Scandinavian Journal of Haematology 29, 147-152 and Eriksson et al, 1989, Journal of Infectious Diseases 21, 434-441). The clinical implications of these limitations are illustrated by a Canadian study (Kain et al., 1998, Clinics in Infectious Diseases 27, 142-149) that reported an initially missed diagnosis in 59% of returning travelers with malaria. The consequent average delay before correct diagnosis and initiation of appropriate therapy was 7.6 days for Plasmodium falciparum and 5.1 days for P. vivax. Such delays can be an important contributory factor to the development of severe malarial complications and mortality rates (Humar et al., 1997, Canadian Medical association Journal 156, 1165-1167).
Malaria was shown to result in leukocyte alterations, reflected mainly by the presence of hemazoin-containing pigments, produced by the various plasmodium species and eventually phagocytosed by neutrophils (Amodu, et al., 1997, East African Medical Journal 74, 714-716) and monocytes (Amodu, et al., 1997, East African Medical Journal 74, 714-716; Amodu, et al. 1998, Transactions of the Royal Society of Tropical Medicine and Hygiene 92, 54-56; Arese et al, 1997, Annals of Tropical and Medical Parasitology 91, 510-516). These changes were recently analyzed for providing an automated diagnosis of malaria, either by means of a flow cytometer (Krämer, et al., 2001, Cytometry 45, 133-140), or of a haematology analyzer measuring light depolarization at two wavelengths (Hänscheid, et al., 1999, Emerging Infectious Diseases 5, 836-838; Mendelow, et al., 1999, British Journal of Haematology 104, 499-503; Hänscheid, et al, 2000, Parasitology Today 16, 549-551; Hänscheid, et al., 2001, American Journal of Tropical Medicine 64, 190-192; Grobusch, et al., 2003, Cytometry part B (clinical cytometry) 55B, 46-51; Scott, et al., 2003, Clinical and Laboratory Haematology 25, 77-86).
It is desirable to be able to detect malaria on an existing hematology analyzer during a blood analysis regularly performed on the instrument, which can assist an earlier detection of the disease without additional cost. Any improved diagnosis and earlier detection can lead to a significant reduction in patient morbidity and mortality.